| In order to cope with the increasingly serious energy crisis and environmental pollution problems,the construction of a new power system with wind and solar as the main body has become an important strategy for the development of China’s electric power industry.At the level of distribution network,the proportion of distributed energy resources is increasing,which affects the safety,stability and economic operation of traditional AC distribution network.The AC/DC hybrid distribution network has the outstanding advantages of convenient distributed energy resources and new load access,flexible topology and strong scalability,which has become the development trend of the distribution network in the future.This thesis studies the optimization operation method of AC/DC hybrid distribution network under the background of high proportion distributed energy resources access,and the main contents are as follows:The networking mode of AC/DC hybrid distribution network and the typical topology of DC distribution network are introduced,the steady-state model of two-level VSC converter station and its linearized operation characteristic equation are established,and the working principle and basic model of AC-DC hybrid distribution network with multiple types of distributed energy access are analyzed.Aiming at the typical radial structure of AC/DC hybrid distribution network,a multi-resource coordinated optimization operation method considering dynamic network reconstruction is proposed.Firstly,a model for dynamic reconstruction of distribution network is established,and in-depth mining and analysis of various types of dispatchable resources at the distribution network level is carried out.On this basis,a two-stage active-reactive power joint optimization operation model is proposed,the first stage takes the lowest comprehensive operation cost of the distribution network and the dynamic network reconstruction cost as the objective function,optimizes the network topology according to the Day-ahead predicted values of wind,solar and load,and takes the lowest comprehensive operating cost of the distribution network as the objective function,and further optimizes the output of other types of active and reactive resources according to the intraday predicted value.The convex transformation of the model is carried out by the sexualization method.Finally,the effectiveness of the proposed model is verified by the improved IEEE50-node AC/DC hybrid distribution network example.Aiming at the AC/DC hybrid distribution network with obvious zoning characteristics and large-scale scalability,in order to overcome the power information transmission limitation caused by different stakeholders of each subsystem and the difficulties faced by centralized method solving,a distributed optimization operation method based on the improved analytical target cascading method is proposed.Firstly,for the DC and VSC converter stations and AC areas in the AC/DC hybrid distribution network,an optimization operation model with the lowest operating cost as the objective function is established,and the optimization variables include the dispatchable resources of its own region and the interactive power between regions.Secondly,the idea of distributed optimization is adopted,the interactive power is used as a shared variable,the objective function is decoupled,and the balance coefficient is introduced into the traditional analytical target cascading method to solve the problem of poor algorithm performance under the condition of improper selection of the initial value of the penalty multiplier and the imbalance between the weight of the subsystem function term and the penalty term,and iteratively solve the distributed model under the consistency constraint.Finally,through the example of distributed AC/DC hybrid distribution network,the effectiveness of the model,the improvement of algorithm performance,and the versatility of the model after network scale expansion are verified. |
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